This invention pertains generally to valves and more particularly to valves for use in ultra high vacuum systems, e.g. vacuum pressures on the order of 10.sup.-.sup.9 torr.
Valves heretofore provided for use in vacuum systems have included right angle valves and gate valves. In right angle valves the inlet and outlet are disposed normally of each other, and closure of the valve is commonly effected by pressing a seal into a seat by means of a screw. The force exerted by the screw generally assures an effective seal, but valves of this type are relatively slow in operation. Moreover, they are usually larger than gate valves of equivalent line size, and they are awkward to use in in-line systems.
Gate valves are well suited for use in in-line systems, and they have the additional advantage that rigid objects can be passed through them if desired.
Gate valves heretofore provided for high vacuum systems have been subject to certain disadvantages, however. The majority of these valves have utilized elastomeric seals which cannot withstand the high temperatures, e.g. 250.degree. C., to which vacuum systems are commonly heated in a bake out process to remove gas and facilitate the reduction of pressure. An all metal valve is better suited for the bake out process, but metal seals require substantially more force to provide a fluid tight seal than elastomeric seals, and gate valves of the prior art have not been able to withstand the necessary force. Moreover, in many prior art gate valves the valve member slides into alignment with the valve openings, and the actuator must travel a distance greater than the diameter of the openings to operate the valve.